<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .wrapper,
    .item {
      border: 1px solid red;
      box-sizing: border-box;
    }

    .wrapper {
      display: flex;
      flex-wrap: wrap;
      width: 902px;
      margin: auto;
    }

    .item {
      height: 300px;
      flex-basis: 300px;
      display: flex;
      justify-content: center;
      align-items: center;
    }
  </style>
</head>
<body>
  <div class="wrapper">
    <div class="item">1</div>
    <div class="item">2</div>
    <div class="item">3</div>
    <div class="item">4</div>
    <div class="item">5</div>
    <div class="item">6</div>
    <div class="item">7</div>
    <div class="item">8</div>
    <div class="item">9</div>
  </div>

  <script>
    !function(){
      let dragDiv = null
      const dragstart =  (e)=>{
        dragDiv = e.target
      }

      const drop = (e)=>{
        [e.target.innerText,dragDiv.innerText] = [dragDiv.innerText,e.target.innerText]
      }

      const dragover = (e)=>{
        e.preventDefault()
      }

      let divs = document.querySelectorAll('.item')

      divs.forEach(item=>{
        item.draggable = true
        item.ondragstart = dragstart
        item.ondrop = drop
        item.ondragover = dragover
      })
    }()



  </script>
</body>
</html>